The Fischer-Tropsch synthesis first began with the development of a technique that produced synthetic fuels from syngas by gasification of coal, by German chemists Fischer and Tropsch in 1923. The Fischer-Tropsch synthesis is a reaction that converts syngas to hydrocarbons in the presence of a catalyst. Herein, an increase in the selectivity of the catalyst used may increase the productivity of hydrocarbons having at least 5 carbons (C5+ hydrocarbons), an indicator of general productivity, thereby increasing the overall carbon efficiency.
Group VIII metals such as iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), and the like have been reported as materials that show activity for the Fischer-Tropsch synthesis. Among them, iron (Fe)-based catalysts have been recognized as beneficial due to their low preparation cost, superior performance, and activity for water-gas shift (WGS), specifically in the Fischer-Tropsch synthesis affiliated with indirect coal liquefaction.
Generally, catalysts used for the Fischer-Tropsch synthesis do not show any activity when in an as-prepared state. Accordingly, the catalysts need to be converted to an active state via reduction (activation) under appropriate conditions prior to synthesis.
Iron-based carbides have been known as a main active species in the iron-based catalysts, and various structures of metal/carbide/oxide are prepared complicatedly during reduction and reaction. Accordingly, when the iron-based catalysts were compared with Co—, Ni—, and Ru-based catalysts, which were merely used as metal active species, the performance thereof was highly dependent on the reduction conditions, and studies to simply increase the amount of iron-based carbides in catalysts showed limited improvement of catalyst performance. Specifically, the conventional studies showed limitations in inhibiting the formation of the unwanted byproducts CO2, CH4, and C2 to C4 hydrocarbons, and increasing the productivity of liquid hydrocarbons having at least 5 carbons (C5+).